1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display module, a liquid crystal display device, and a method for assembling the liquid crystal display device, which can minimize the overall size of the liquid crystal display device by improving the engaging structure of the liquid crystal display module and a case.
2. Description of the Related Art
Recently, an information processing device has been developed to have a various shape, a various function, and a rapid information processing speed. The information processed in the information processing device is represented as electrical signals. In order to figure out the information processed in the information processing device for a human being, a display device is needed as interface.
Recently, a liquid crystal display device that is lighter, and smaller than a CRT type display device has been developed. The liquid crystal display device has a function such as a full color and a high resolution. As a result, the liquid crystal display device is widely used as a monitor of a computer, a television, and another display device.
The liquid crystal display device applies voltages a layer of liquid crystal to convert the molecular arrangement to another molecular arrangement. The liquid crystal display device converts the changes of optical properties to visional changes and uses the modulation of a light by using a liquid crystal cell.
Liquid crystal display devices are sorted to a TN (Twisted Nematic) device and an STN (Super-Twisted Nematic) device, and are sorted to an active matrix display that uses a switching device and a TN liquid crystal and a passive matrix display that uses a STN liquid crystal according to the driving type.
The active matrix display is used in a TFT-LCD and drives an LCD by using a TFT as a switch. The passive matrix display does not use any transistor and does not need a complex circuit.
Further, liquid crystal display devices are sorted to a transmitive liquid crystal display device that uses a back light and a reflective liquid crystal display device that uses an exterior light source depending on the way of getting a light source.
The transmitive liquid crystal display device that uses the back light as a light source is heavy and voluminous due to the existence of the back light, but is widely used since it displays independently without using an outside light source.
FIG. 1 is an exploded perspective view for schematically showing a conventional liquid crystal display device. FIG. 2 is a partial exploded perspective view of the liquid crystal display device shown in FIG. 1.
Referring to FIG. 1, the liquid crystal display device 900 has a liquid crystal display module 700 to which an image signals is applied to display the screen, and a front surface case 810 and a rear surface case 820 that receive the liquid crystal display module 700.
The liquid crystal display module 700 has a display unit 710 that comprises a liquid crystal display panel.
The display unit 710 has a liquid crystal display panel 710, an integrated printed circuit board 714, a data side tape carrier package 716, and a gate side flexible circuit board 718 manufactured by the COF method.
The liquid crystal display panel 712 has a thin film transistor substrate 712a, a color filter substrate 712b, and a liquid crystal layer between (not shown).
The thin film transistor substrate 712a is a transparent glass substrate in which thin film transistors of a matrix type are formed. Data lines are connected to source terminals of the thin film transistors, and gate lines are connected to gate terminals of the thin film transistors. Pixel electrodes of indium tin oxide (ITO), which is a transparent conductive material, are formed in drain terminals.
If electrical signals are inputted to the data lines and the gate lines, the electrical signals are inputted to the source terminals and the gate terminals of thin film transistors and the thin film transistors are turned on or off so that electrical signals needed for forming pixels are outputted to the drain terminals.
The color filter substrate 712b is opposite to the thin film transistor substrate 712a. RGB pixels through which a light is passed to realize a color is formed in the color filter substrate 712b by a thin film process. A common electrode of ITO is laid on the color filter substrate 712b. 
If a voltage is applied to the gate terminals and the source terminals of the transistors and the thin film transistors are turned on, an electric field is formed between the pixel electrode and the common electrode of the color filter substrate. The arrangement of the liquid crystals injected between the thin film transistor substrate 712a and the color filter substrate 712b changes by the electric field, and the transmittance of light changes as the arrangement changes.
A driving signal and a timing signal is applied to the gate line and the data line of the thin film transistor to control the arrangement of the liquid crystal of the liquid crystal display panel 712 and the timing of when the liquid crystal is arranged. The data side tape carrier package 716 which is a kind of flexible circuit board that determines the timing when the data driving signal is applied is attached to the source side of the liquid crystal display panel 712, and the gate side flexible circuit board 718 manufactured by the COF method for determining the time at which the gate driving signal is applied is attached to the gate side of the liquid crystal display panel 212.
The integrated printed circuit board 714 for receiving image signals from outside of the liquid crystal display panel 712 and applying driving signal to the gate line and the data line is connected to the data tape carrier package 714 of the data line side of the liquid crystal display panel 712. The integrated printed circuit board 714 has a source part to which the image signals generated in an exterior information processing device (not shown) such as a computer are applied to provide the data driving signals to the liquid crystal display panel 712 and a gate portion for providing the gate driving signals to the gate line of the liquid crystal display panel 712. Namely, the integrated printed circuit board 714 generates the gate driving signals for driving the liquid crystal display device, the data signals, and a plurality of timing signals for applying the signals at a proper time. The gate signals are applied to the gate line of the liquid crystal display panel 712 through the gate side flexible circuit board 718, and the data signals are applied to the data line of the liquid crystal display panel 712 through the data tape carrier package 716.
A back light assembly 720 that provides a uniform light to the display unit 710 is located under the display unit 710. The back light assembly 720 has a linear lamp 722 on one side of the liquid crystal display module 700 to provide the light. A light guide plate 724 has a size corresponding to the liquid crystal display panel 712 of the display unit 710, and is located under the liquid crystal display panel 712. The lamp side of the light guide plate 724 is the thickest. The thickness gradually decreases as goes away from the lamp 722. The light guide plate 724 guides the light generated in the lamp 722 towards the display unit 710, and changes the passage of the light.
A plurality of optical sheets 726 that spread and intensify the light and pass it towards the liquid crystal display panel 712 are provided above the light guide plate 724. A reflection plate 728 provided under the light guide plate 724 reflects the light leaking from the light guide plate 724 and promotes the efficient use of the light.
The display unit 710 and the back light assembly 720 is fixed and supported by a mold frame 730 which is a receiving receptacle. The mold frame 730 has a box-shape, and the upper surface of the mold frame 730 is open. Namely, the mold frame 730 has four side walls and a bottom surface. And openings for bending the integrated printed circuit board 714 along the outer side surface of the mold frame 730 and for positioning the integrated printed circuit board 714 are formed on the back of the bottom surface.
A chassis 740 for bending the integrated printed circuit board 714 of the display unit 710 and the gate tape carrier package 718 outside of the mold frame 730 and fixing the integrated printed circuit board 714 of the display unit 710 and the gate tape carrier package 718 to the bottom surface of the mold frame 730 to prevent the deviation of the display unit is provided. The chassis 740 has a box-shape. The upper surface of the chassis 740 is open to expose the liquid crystal display panel 710, and the side walls are bent inwardly to cover the upper surface peripheral portion of the liquid crystal display panel 710.
On the other hand, referring to FIG. 2, a plurality of protruding portions 731, 733, 735, and 737 for engaging the mold frame 730 to the front case is formed on the outer surfaces of the opposite side walls of the mold frame 730, and engaging holes 731a, 733a, 735a, and 737a are formed in the protruding portions 731, 733, 735, and 737. Bosses (not shown) having nut portions (not shown) are formed on the bottom surface of the front case so that screws 750, 753, 755, and 757 are engaged through the engaging holes 731a, 733a, 735a, and 737a at positions corresponding to the protruding portions 731, 733, 735, and 737.
However, if the mold frame 730 is engaged with the front case 810 in the above-mentioned manner, the sizes of the front case 810 and the rear case 820 are increased by the length of the protruding portions 731, 733, 735, and 737. Therefore, the overall size of the liquid crystal display device 900 increases.